1. Field of the Invention
The invention relates to the field of microprocessors and microprocessor systems. More particularly, it relates to the field of making internally known access information of a microprocessor available to external circuits of a microprocessor system.
2. Description of Relevant Art
Methods for signalling whether a code or data access is being made to an external memory by a microprocessor are known in the art. One method relies on creating or devoting an entire separate signal pin to indicate the access type. The Intel 80386.TM. CPU uses such a method. A "D/C#" pin specifies whether code or data is being accessed from external memory by the microprocessor. This method, however, requires an additional pin which is expensive and in limited supply on microprocessors.
A different method to relay the code/data information is employed by present microprocessors such as the Motorola 68000 and the Intel 80286. These microprocessors encode the information on a group of signal pins devoted to cycle type information. The Motorola 68000 encodes the information on FC2, FC1 and FC0 while the Intel 80286 encodes the information on pins S0 and S1. However, cycle type encoded information is not liked by users.